This invention relates to the extraction of metals from ore and particularly exotic and/or precious metals such as gold, silver, platinum, palladium, iridium, and others, which are most often available in a mixture or alloy thereof. The metallic values which are sought for are found in a premetallic crystalline state, a metallic state, and a postmetallic isotopic state; and the complexity of ores varies greatly in this respect. Although there are various methods of extracting ores, it is often difficult and sometimes impossible to extract the desired metals on an economically practical basis, and in some instances not at all. In practice, the usual methods of smelting and leaching ores for their metal values does not produce 100% recovery, and the tailings retain measureably high values of metals. Therefore, it is an object of this invention to provide an improved method and apparatus for the substantially complete (90%-100%) extraction of metals from ore.
The reduction of metals from ore follows many processes, some of which are very efficient. However, there are vast quantities of tailings available from smelters and the like that are rich in precious metals; also, there are vast quantities of virgin ores that are rich in precious metals; and yet in many instances there has been no practical method for substantially complete extraction thereof. And further, there are tailings and virgin ores that cannot be assayed to show any metallic values, but which show color bands indicating metals when exposed on a spectograph. It is these marginal tailings and ores with which the present invention is particularly concerned, it being a general object of this invention to extract metallic values from tailings and ores which have heretofore assayed as economically valueless.
Smelting of ores is usually conducted in a furnace wherein high heat is directly or indirectly applied. There are of course advantages to be gained by the various indirect and direct heat methods, which need not be discussed here, and the application of electrical energy applied directly as an arc from or between electrodes is well known. However, the violence of energy application in an electric arc furnace, for example, is destructive of the metals by vaporization, and to this end the discharge of electrical energy for these purposes has been conducted in a slurry of the ore to be reduced. For example, ores are reduced to their metallic values by intermittently striking a high frequency electrical arc through a slurry of the ore and along a path between electrodes. And though it is possible to extract solid state metals in this way, the percentage of reduction is limited because of the localized application of the electrical arc. In other words, the total mass of the ore is not completely subjected by the prior art processes. However, with the present invention a substantially complete subjection is attained, it being an object of this invention to provide a method and apparatus for the substantially complete subjection of ores to the smelting effect of electrical energy discharged therethrough. With the present invention, electrical discharges are distributed over a determinable area and through a layer of ore coextensive with said area, and to the end that substantially complete subjection is attained.
The discharge of high intensity electrical arcs through a slurry of ore has been practiced for the reduction of metals in a cooling environment. It has been theorized that the "slurry" of a thin mixture of water and of the many fine insoluble materials comprising the ore, condenses by vaporization and cools the reduced metals to a solid state. It has also been theorized that the slurry of ore subjects the premetallic as well as postmetallic state of the metal values to the electrical arc for a change of electrons which produces solid state metals. And, the application of electrical energy has been made at or near the natural frequency of the metal to be reduced, so that the metal theoretically assumes a stable state. With the present invention, a "slurry" as such is not employed in the strict sense of a mixture of water and fine insoluble ore. In contradistinction, a layer of ore is deposed upon the surface of an electrode and contacted by or exposed to an electrode of opposite polarity. This contact or exposure can be conducted openly or through a protective fluid in which it is immersed. Thus, a preadmixture of water and ore is not requisite of the present invention. A cover of protective gas or liquid is provided over the layer of ore through which electrical enery is coextensively applied. Therefore, it is an object of the present invention to maintain a layer of ore for reduction separate from an enveloping cover of protective fluid such as water.
The discharge of electrical energy in arc furnaces and the like has been localized and confined to the alignment of the electrodes that strike an arc from point to point. Generally, electrodes for this purpose have been elongated elements projected into aligned spaced opposition as anode and cathode. With the present invention, the anode and cathode are flat faced and opposed positive and negative plates, brought into contact with the pulverized granules of ore, or spaced with the layer of ore therebetween in which case at least one of which is serrated so as to present a multiplicity of discharge peaks disposed uniformly from the other electrode; it being an object to provide energy discharges at random coextensively between said two electrodes. In practice, the lowermost electrode is a flat supporting surface for the ore, while the uppermost electrode has a flat surface that rides upon the ore, or is spaced therefrom and is serrated for random electrical arc discharge.
The transport of ore by the method and through the apparatus is such as to pass all ore between the two aforementioned electrodes for substantially complete subjection to the high heat of electrical energy discharged randomly between said electrodes. Accordingly, the lowermost electrode is the conveyor which receives the pulverized ore and passes the same in a layer beneath the other electrode superimposed thereover to provide passage therebetween. Therefore, it is an object to provide means to convey ore for its coextensive subjection to electrical energy flowing between spaced electrodes. It is another object to provide for the conveyance of ore upon an electrode while immersed and/or submerged in a protective fluid. It is still another object to provide for the discharge of processed ore while maintaining the protective fluid over the same.
The susceptibility of ores to the effect of electrical discharges can be improved, as has been discovered in practicing the present invention; and accordingly the ore is ionized by removing one ion precedent to introduction between the active electrodes. Further, the use of electronic control circuits enables the conduction of electrical impulses through the ore particles with a balancing of the voltage and amperage factors and by control of the frequencies to coincide with the resonant frequencies best suited to react on the various metallic values. Accordingly, it is still another object of this invention to provide electronic means to ionize and also to control the voltage, amperage and frequencies of the electrical discharges at random from the superimposed electrode.